Force icu4c to always default to the Gregorian calendar.
This matches the Java side of the system (and pre-KitKat behavior).
Bug: 12004664
(cherry-picked from b844b3e14e24df5b8d9b25539f6eb92ac507d8b4)
Change-Id: I2462e9a8af288535a1511f7cb3bba9dd459a8ed3